The field effect transistor is to use semiconductor surface effect, to control the depletion or accumulation of the semiconductor active layer surface hole and electron with the gate voltage to determine the channel conduction condition and to achieve the switching function. The principle of the field effect transistor is simple. The process is mature and reliable. The field effect transistor is widely used in the manufacture of electronic elements and integrated circuits. The performance of the field effect transistor is determined by many factors, such as skill, process, material and element structure. The channel material and element structure fundamentally determine the mobility and the working efficiency of the field effect transistor.
The two-dimensional nanomaterials such as grapheme and transition metal sulfide have shown the extraordinary application potential with the excellent physical property and the structural property in the fields of the electronics, sensors and optoelectronic elements. The graphene as the most representative two-dimensional material has been extensively studied. It has an ultra high carrier mobility but the lack of the band gap has seriously hindered the application of graphene in semiconductor elements, such as field effect transistors. The disulfide bonds in the transition metal sulfide have a significant band gap and show excellent on off ratio properties in the transistor. However, the structural defects of the disulfide bonds may lead to a reduction in electron mobility, which affects the electrical properties thereof. Thus, the method of introducing a band gap in graphene is used.
The black phosphorus has attracted much attention from the scientific community because of the excellent performance. It has a wave layer structure, which is similar to but different from the graphene sheet structure and has a semiconductor gap that the graphene does not have. More importantly, its semiconductor band gap is a direct band gap. Namely, the electronically conductive energy band is at the same location as the nonconductive energy band top. Accordingly, it is considered as the super material in the two-dimensional materials by the scientific community. Meanwhile, due to quantum confinement effect, the black phosphorus quantum dots possesses have more excellent photoelectric properties than the black phosphorus block materials and can be widely used in the field of photovoltaic application and transistor application.